Polymeric carbon and method of production



United States Patent POLYMERIC CARBON AND LET HOD OF PRODUCTION GilbertB, Carpenter, Mountain Lakes, Edward R. Blanchard, Summit, and Alio J.Buselli, New Providence, N. IL, assignors to Air Reduction Company,Incorporated, New York, N. Y., a corporation of New York No Drawing.Application March 23, 1951}, Serial No. 344,215

9 Claims. (Cl. 260-666) This invention relates to new chemical productsand Patented Oct. 2, 1956 "ice portional to temperature up to about 540C. The inrease in density when heated above about 540 C. is very slightalthough the other properties change appreciably as the productprogressively changes to a'struc ture having some of the characteristicsof diamond.

344,216, filed March 23, 1,953.

m th n ha f r i bj the Provision f poly- Table I which follows shows theefiectsof heating molde and non-molded polyacetylene at difierenttemperatures, periods, and in the presence of difierent gases atatmospheric pressure:

TABLE I Efiect of temperature on poiyacetylene Run No Polymer FormAtmos- Max. t., Time at Wt. Loss, Remarks, phere C, t., 0. Bement 30096.0 Black ash. 200 +4. 3 Retained s ape and cele 450 14. No apparentchange. 450 .33. 3. Turned 'hlackrretainedshape. 250 81.3 Partiallyashed; lost shape. 450 4. 5 Retained shape;-edges-split. 450 12; 7Blackened and cracked.

.--do 450 2.4. 0 Blackened bntretal edshape. Powdered (1150.. 450 40. 0Black; some ashing. Unmolded 700 17.5 arlrened.

Molded disc"--- N 700 24. 9 Noticeable shrinkage of disc.

d 340 1 hr 1. 5 No chauge.

360 1 hr 8.1 Do. 380 1 hr 0 D0. 400 1 hr 3. 6 Do. 450 1.5 h 11.3 Darkened;.1o ss 11 diameter. 525 1.5 hr 22. o Do. 500 1 hr----- 18.7- Do.580 1 hr..... :13. 9 D sc was dark and cracked 550 2 hrs 23. 2 Discshowed loss in diameter and darkened.

700 2.5 hrs 24. 9 Good disc reduced in size. see 15 25. no,- 900 3 hrs.24. 8 Good disc 1%" in diameter. 325 miu 3.05 1 Small 1055 in diamet r..325 15 min.. 3.05 No change. 400 1 hr----- 7.17 1 Do. 650 :1 hr 125. 6Darkened. 700 1'hr-- 25.8 v Do.

meric carbon and a method of producing the carbon. More particularly,the invention provides polymeric carbon formed by dehydrogenation ofpolyacetylene, a polymer known as cuprene or carbene. The polymericcarbon is characterized by chemical stability and inertness and bygreater density and electrical conductivity than the polymer.

This invention is based upon the discovery that volatile degradationproducts can be removed from polyacetylene at temperatures above 320 C.when the polyacetylene is protected by the use of a vacuum or an inertgas, such as nitrogen or argon. When polyacetylene is heated whilesuitably protected, it appears to be relatively stable up to 320 C. Asthe temperature is increased, the polymer undergoes a progressivedegradation manifested by a loss of volatile matter and an increase indensity. The degree of this degradation is almost linearly pro- In Runs3, 4, 6, 7, 8 and 9, the nitrogen was 99.8% N2 plus argon and a smallamount of 02.

In Runs 10 to 28 purified nitrogen was used which contained about 99.9%N2 and substantially no 02.

In Run No. 11 a Dry Ice trap was attached to the exit stream in order totrap out the higher boiling volatiles. Material corresponding to aweight loss of 17.5% was collected in the trap. On warming thecondensate to room temperature, the material appeared to be anonvolatile oily liquid which did not decolorize bromine in carbontetrachloride. Assuming that the loss of weight noted in the finalanalysis was due mainly to the cracking of C-H bonds, then the maximumamount of low boiling material, such as methane, ethane, ethylene andacetylene, amounts to about of the total weight lost. The density asmeasured by Archimedes Principle on the products of Run Nos. 27 and 28was observed to change from approximately 0.92 before heating to 1.46after heating which is equivalent to a density of about 1.5.

Table II shows that the loss of weight corresponds Analysis of the finalproduct shows that about 80-90% of the hydrogen in the polymer is lostduring the heating process. Two samples heated to 700 C. had thefollowing analysis: I

Per- Per- C/H C/H Sample No. Form cent .0 centH Final Average FinalFinal Initial 1 Unmolded 89.8 0.78 9.6 1.25 2 Moldeddlsc. 95.8 1.20 :Sql1.25

Polyacetylene has high'dielectric properties and:ca'n-' notbeconsideredas .anelectrical conductor. The polymeric carbon of the inventionresulting from the deg radation of the polymer is an electricalconductor the resistivity ofwhich-"can be "controlled by the degree ofdegradation, and because of its high rc'sis'tivity is an efiectiveresistor for many purposes.

The dielectric constant of polyacetylene is comparable to themethacrylates and hard rubber, better than the phenolics, but not asgood as polystyrene or polyethylene.

By efiecting dehydrogenation progressively in increments a series ofelectrical resistors and electronic semi-conduc--- tors of graduatedresistivity can be produced.

For example, the polymer has a volume resistivity 10 ohm-cm. Whenjthepolymer is heated, weight losses of 'l8%, 2-3 and 25% result inresistivity values value approximately equals the graphite.

We claim:' I a conductivity 1. Shaped articles formed of polymericcarbon pro duced essentially byheating molded articles of cuprene--- 2.The method of forming -polymeric carbon which consists essentiallyof"heating;cuprene'iri an. inert atmosphere 'a't'a'temperature above 320C. to effect dehydrogenation.

3. In the method of claim 2 heating a molded cuprene article.

4. In the method of claim 2 heating the cuprene in an atmosphere ofnitrogen.

5. In the method of claim 2 heating the cuprene in an atmosphere ofargon.

6. Polymeric carbon prepared essentially by heating cuprene in an inertatmosphere to a temperature of from about 320 C. to about 900 C., saidpolymeric carbon having a ratio of carbon atoms to hydrogen atoms ofabout 8:1 to about 10:1 and about 0.787 to 1.20% hydrogen, and having anelectrical volume resistivity of from about 10 ohm-cm. to about 10ohm-cm.

7. The method of forming polymeric carbon having an electrical volumeresistivity of from 10 ohm-cm. to about 10 ohm-cm. which consistsessentially of heating cuprene in an inert atmosphere at a temperatureof from about 320 C. to about 900 C. to effect dehydrogenation, andselecting the particular temperature employed so that a polymeric carbonis obtained having a desired electrical volume'resistivity within theaforesaid range.

8. A shaped article of polymeric carbon having an electrical volumeresistivity of from 10 ohm-cm. to aboutl0 ohm-cm. prepared essentiallyby heating a molded article ofcuprene in an inert atmosphere 'at atemperature of from about 320 C. to about 900 C., and where the heatingtemperature was selected so that the desired electrical volumeresistivity is within the aforesaid range.

9. The method of forming polymeric carbon having an electricalvolumeresistivity of from 10 ohm-cm. to about 10 ohm-cm. which consistsessentially of heating cuprene in an inert atmosphere at a temperatureof from "above'about 320 C. up to about 540 C. to effectdehydrogenation, and selecting the particular temperature employed sothat a polymeric carbon is obtained having I a desired electrical volumeresistivity within the aforesaid range.

References Cited in the file of this patent UNITED STATES PATENTS2,453,440 Kaufmann Nov. 9, 1948 2,582,764 Bailey Jan. 15, 1952 2,697,028Baker et a1. Dec. 14, 1954 FOREIGN PATENTS 20,851 Holland Nov. 15, 1929OTHER REFERENCES Ellis& The Chemistry of Synthetic Resins, vol. 1, pages142-147 (1935), Reinhold Publishing Corp,

in an inert atmosphrefto -a temperature above 320 Cifjj New'York.

Calhoun: Canadian Journal of Research, vol. 15B

1. SHAPED ARTICLES FORMED OF POLYMERIC CARBON PRODUCED ESSENTIALLY BYHEATING MOILDED ARTICLES OF CUPRENE IN AN INERT ATMOSPHERE TO ATEMPERATURE ABOVE 320* C.